Combination mechanical-thermal latch



v Oct 1968 c. L. ANDERSQN 3,406,677

0M INATIQ Filed June 30. 1966 2 Sheets-Sheet l r 38 39 U T 1 .5 2 D 2 .5 I, 2 9 3 28 52 2 lb 9 In F" 4 "lj I' 20 2. M 4 44 I II .4 "ml 8 22 H I 5|TL I 2 53 A MENTOR E5 L. NDERSON ATTORNEYS ,1968 c. ANDERSON 3,406,677

COMBINATION MECHANICAL- THERMAL LATCH Filed June 30, 1966 2 Sheets-Sheet 2 lul W I" "m "Wk 39 L i 5 3V A Ml/ 57 7/ 41 INVENTOR CARL L. ANDERSON ATTORNEYS United States Patent 3,406,677 COMBINATION MECHANICAL-THERMAL LATCH Carl L. Anderson, Shiloh, Ohio, assignor to The Tappan Company, Mansfield, Ohio, a corporation of Ohio Filed June 30, 1966, Ser. No. 561,851 Claims. (Cl. 126197) ABSTRACT OF THE DISCLOSURE A combination mechanical-thermal latch for the door of a high temperature oven including a manually actuated handle movable between latched and unlatched positions and a rotatable lock arm movable into arresting engagement with the handle when latched to preclude opening of the latch mechanism. The lock arm is driven rotatably by a spiral bimetal element positioned adjacent an opening in the oven to respond to the temperature of the latter. The bimetal is designed to actuate the lock arm into the handle locking condition when the oven temperature is above a predetermined degree.

This invention relates to improved latch mechanism in which mechanical and thermal actuation modes are combined and, more particularly, to such a latch in which temperature is in factor in the release or unlatching action thereof.

The new latch was developed for and will be described in association with the door of an oven of the automatic cleaning type which has recently become available for use in the home and in which the cleaning is accomplished by heating to a temperature above the normal cooking temperature range to consume soil on the interior surfaces of the oven. The oven temperature in such a cleaning operation will generally be above 750 F. and there should desirably be some protection against inadvertent opening while such a high heating condition exists. Such a safety feature is provided by the thermal actuating mode of the latch mechanism of this invention in its noted restriction of the mechanical unlatching action.

It is a further object of the invention to provide a combination mechanical-thermal latch for doors or other closures of ovens and comparable heating cavities of a simple and highly reliable configuration, with the design moreover such that accidental jamming of the mechanism is not possible. In this last connection, it has been found that at least certain types of door latches provided with ovens as indicated are quite susceptible to jamming by inadvertent striking of the operating handle used and projecting forwardly at the top front of the range cabinet. Such jamming not only results in considerable inconvenience to the housewife, the construction is such that the repair is a difficult and time-consuming job for even a service man trained in the maintenance and repair of the range.

It is a further object to provide such a combination latch having a temperature responsive element which is adjustable for selection of the particular temperature at which it is effective or operative in the intended manner, the design being such that this adjustment can very readily and conveniently be made.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

3,406,677 Patented Oct. 22, 1968 In said annexed drawings:

FIG. 1 is a perspective view of a range in which the new latch mechanism is incorporated for the oven door;

FIG. 2 is a fragmentary transverse sectional view of the range on an enlarged scale and showing in particular the door latch mechanism;

FIG. 3 is a horizontal sectional view from a plane above and looking down on the latch as indicated by the line 33 in FIG. 2; and

FIG. 4 is a view similar to FIG. 3 but showing the latch moved to another condition of adjustment.

Referring now to the drawings in detail, the domestic cooking range designated generally by reference numeral 10 in FIG. 1 is of known construction and manner of operation apart from the latch mechanism for the door which constitutes the subject matter of the present invention. This particular range is of electric type and thus comprises surface heaters 11 in the conventional form of sheathed electric resistance heating elements and an oven 12 of the design used for automatic cleaning and having the usual top and bottom resistance heating elements. It will be apparent that these features are not critically related to the new latch but provide, as an environment, a heating cavity having an access opening closed by a door 13 which is itself also of standard construction for such an oven except for the portion at which the latch mechanism is operative.

The upper portion of the oven is shown in FIG. 2 as comprising a top wall 14 spaced appreciably below the bottom of the burner box 15 which contains the surface elements and controls 16 and this space will be filled with suitable heat insulating material, such as glass wool, not shown. A vertical framing wall 17 bridges between the burner box and oven top across the front, and it will be understood that there will be comparable framing of the oven front at the sides as well.

The door 13, which is hollow and will also contain heat insulation, comprises outer and inner walls 18 and 19 the latter of which is formed with an inward offset 20 which confronts the upturned forward edge 21 of the oven top 14 when the door is closed as shown and a suitable gasket 22 is interposed between these surfaces and the comparable surfaces at the sides of the oven. A latch pin 24 is held vertically within the door beneath the top center by a mounting bracket 25. The inner wall 19 of the door has a horizontal slot 26 in its portion adjacent the pin 24 to expose the latter for a purpose to be described.

The new latch mechanism is supported on a mounting plate 27 within the burner box 15 and at the front just behind the upper portion of the vertical front oven frame member 17. A vertical bolt 28 through the plate serves as a common pivot for a latch finger 29 disposed against the underside of the plate and an operating lever 30 on the upper plate surface. Behind the bolt 28, the plate is provided with an appreciable opening 31, and a roller 32 is mounted on the inner end of the finger 29 and projects upwardly through this opening of the plate for engagement with the rear edge of the operating lever 30 as illus trated. The finger 29 has a longitudinal slot 33 at its attachment to the bolt 28 so that it can experience in and out movement relative to the plate, and a coil spring 34 exends between a forward anchor point on the plate and the stem on which the roller 32 is rotatably mounted to exert a forward bias and thus resiliently hold the roller against the lever 30.

At this inner end, the lever 30 is laterally enlarged and shaped so that the rear edge thus engaged by the roller has a relatively raised or extended rounded portion 35 merging with a rounded depression 36, and, adjacent the latter continuing in the same direction, a small upstanding tab or locking dog 37. When viewed from the top, as in FIGS. 3 and 4, it will be seen that this locking dog 37 is at the right inner corner of the lever body enlarge- I ment. The reduced continuation 38 of the lever is upwardly offset by the step 39 and projects forwardly to a noticeably greater extent than the latch finger 29. The latter projects through the oven frame 17 horizontally to enter the slot 26 in the door when closed for engagement with the latch pin 24, the finger having a forward hook end 40. The operating lever will be seen also to project forwardly from the range above the top of the door for actuation of the latch in a manner to be described.

The latch mounting plate 27 also supports a tube 41 rotatably in vertical penetrating relation, with only a relatively small upper end portion above the plate. A lock arm 42 is attached horizontally to a shaft 43 free to rotate or turn within the tube 41. The length of the tube is such that the lower end is within a small domelike wool shield 44 against the outer top 14 of the oven and this end is cut and shaped to terminate in an arm 45 which extends horizontally and then downwardly. A flat spiral bimetallic element 46 is also disposed within the dome 44 and has a bent outer free end hooked on the tube arm 45. This coil is suspended on the shaft 43 to which it is attached at its central inner end, and the shaft extends freely upwardly through the tube 41 and above the upper end of the latter where the lock arm 42 is attached thereto. A wire spring 47 is placed about the upper exposed end of the shaft 43 and has one end anchored and its other end bent over the rear edge of the lock arm 42 as shown. This spring thus acts on the arm 42 to urge or bias such arm forwardly or in a clockwise direction as viewed from above, with the bimetallic coil normally at room temperatures holding the arm against the spring force in the retracted position shown in FIG. 3 through the engagement thereof between tube 41 and the shaft 43.

A small sector shaped plate 48 attached to the tube 41 overlies the top of the mounting plate 27 and this plate has a curved slot 49 through which an attaching screw 50 extends and is threaded in the plate. This means of attachment of the tube to the plate will be seen to permit rotative adjustment of the tube and this is effective to vary the angular position of the tube arm 45 attached to the bimetal coil 46. As will be seen in the following, such adjustment determines the temperature at which the bimetallic thermostat becomes effective in the locking of the operating lever which precludes unlatching.

In the preferred embodiment, the thermal lock is thus effective at oven temperatures in excess of 600 F., the response being established by providing a hole 51 in the oven top 14 just beneath the bimetal coil 46 and above the front edge portion of the broiler shield 52 which extends over the top or broiler heating element 53. The closed door but unlatched condition of the assembly is illustrated in FIG. 3, and it will be seen that the latch finger 29 has entered the door to the side of the latch pin 24, that the roller 32 at its other end is within the relatively depressed edge section 36 of the operating lever 30 for maximum forward projection of the finger, and the locking bar 42 of the thermal actuator is in a relatively retracted position. When the free end of the operating lever is grasped and swung horizontally to the left or in a clockwise direction as viewed from the top, the rear edge of the operating lever cams the roller 32 in the same rotative direction and also inwardly and the resulting translation of the finger 29 causes the hook of the latter to engage about and then firmly draw in against the latch pin 24. In the full mechanically latched condition, the roller is cammed to the rearmost extension shown in FIG. 4 against the force of the biasing spring 34. If the temperature of the oven in the normal use thereof for cooking does not reach the temperature at which the bimetal coil is adjusted for the locking operation, there is no interference with the latch and the door can simply be released by reverse swinging of the operating lever. However, if the temperature within the oven reaches the design level for the thermal locking, the bimetal coil 46 will have relaxed or unwound sufficiently to permit the spring 47 to turn arm 42, and shaft 43, to the position shown in FIG. 4 in which the end shoulder 54 'of this arm is moved behind the locking dog '37 on' the operating lever 30. For as long a's'this condition exists, it will be evident that the lever cannot 'be moved in the unlatching direction. As the temperature drops, however, upon termination of the high heating operation, the bimetal will relatively collapse or contract with turning of shaft 43 to move the arm 42 out of the locking relation to the dog 37, whereupon the housewife or other user can manipulate the handle part of the lever in the usual manner to open the door. 7 v v It is significant to note that the hooking of the bimetallic coil 46 on the arm 44 of the tube 41 is in a direction which permits the hooked coil end to move away from this arm 44 in the expansion or unwinding of thecoil with temperature increase. More particularly, the degree of coil relaxation with heating to the adjusted'temperature setting for the thermal latching is such that the shaft 43 is turned sufficiently by the force of spring 47 to bring arm 42 into the stopped position against the lever dog 37, and further movement of such shaft and arm is of course precluded by this engagement of the lever. The further increase in temperature to the desired maximum for the cleaning action causes the coil to relax further, with such continued relaxation accommodated by the freedom of its hooked other end to move off the tube arm 44. When the cleaning operation is concluded, the resulting contraction of the coil will return the hook end to the anchoring engagement with the tube arm 44 whereby the continued contraction is effective at the other coil end to turn shaft43 and hence locking arm 42 back to unlatched condition. The coil integrity is thus assured and calibration maintained, which would not be possible if the coil experiences strain in its operating mode.

-It may' also be desired to incorporate an electrical switching function for the range responsive to actuation of the door for signal or control purposes, and there is shown for this purpose a microswitch 55 mounted on the plate 27 with an actuating lever 56 in engagement with the roller 32. It will be seen that the movement of the roller in the adjustment of the mechanism from the unlatched to the latched condition causes the lever 56 to be depressed against the spring-biased switch plunger 57, whereby closure of the switch, for example, is dependent upon the full latching of the door. This design, moreover, protects against switch closure in the event of inadvertent or accidental actuation of the lever 56 with the door open, to preclude for example the start of the high temperature cleaning cycle made dependent on such switch closure. it will be seen that the lever cam edge 35 causes the roller 32 to undergo an over-center movement in being cammed from its unlatched position of FIG. 3 to the latched position of FIG. 4, with the latch bar 29 thus brought firmly against the pin 24 of the door when closed. Should the door, however, be open, the lack of the restraint afforded by the engagement with pin 24 permits the roller to move further on the edge 35 and thus relatively forward under the force of the spring 34 and 'bar 29 will spring back, the roller moving also beyond the closing engagement with switch lever 56, so that the switch will only instantaneously be closed in this actuation.

The point at which the thermal lock is effective thus depends upon the degree that the lock arm 42 has to move from its normal position at room temperature to the locking position illustrated in FIG. 4 and the elfective starting point or the room temperature position can be adjusted by loosening the screw 50 and shifting the adjustment plate 48 to turn the tube 41 and the point at which the outer coil end is anchored by hooking on tu'be arm 44. The normal tension in the coil 46 is thus varied, and it has been found in one embodiment that the bimetal will turn the lock arm approximately 110 degrees in becoming heated from room temperature to approximately 600 F.

With further regard to FIG. 4, it will be clear that inadvertent jarring of the operating lever 30 in the latching direction, which is the only direction in which the lever can experience any movement in this condition, will simply cause a degree of resiliently resisted strain without any tendency to jam, the spring 34 yielding and the dog 37 free of the arm 42 in this direction.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

1, therefore, particularly point out and distinctly claim as my invention:

1. In :an electric oven having an upper resistance heating element in close spaced relation below the oven top and a shield interposed between the two, the oven having a door, combination mechanical-thermal latch mechanism for locking the door in the closed position, said mechanism comprising a latching member and a cooperable detent one of which is mounted on the oven structure and the other on the door, actuating means for moving the latching member relative to the detent when the door is closed for laching and unlatching with the detent, and thermal interlock means for preventing unlatching movement of the latching member when the temperature of the oven is above a predetermined degree, said interlock means including a temperature responsive means located externally adjacent an opening in a portion of the oven top above said shield.

2. The combination set forth in claim 1, wherein the manual actuating means comprises an operating lever having a stop surface, and said thermal interlock has a cooperable surface for engagement therewith for the prevention of the unlatching movement of said latching member.

3. The combination set forth in claim 1, wherein the manual actuating means comprises an operating lever, and the latching member is connected to said lever to move both with and relative thereto in the latching and unlatching actions.

4. The combination set forth in claim 1, wherein the temperature responsive means is a bimetallic coil, and the interlock means further includes :a locking element which is rotated by the coil with heating and cooling thereof.

5. In an oven and the like equipped with means for heating the interior thereof and having a door, latch means acting between the oven and door for holding the latter in closed condition and comprising a pivoted latch ing element and cooperable detent means one of which is mounted on the oven and the other on the door, mechanical actuator means including an externally ac cessible pivoted operating lever movable by hand to adjust the latch means between the latched and unlatched conditions, said actuator means including connecting means between the lever and latching element for move ment of the latter with and relative to the former, said connecting means yieldingly holding the lever and element together in a latched and firmly locked condition so that the lever can move relatively to a limited degree in the latching direction, with the lever and element having cooperable cam surfaces causing the element to move correspondingly in direction with the lever, a separately movable locking member normally in non-interfering adjacency to the path of movement of the lever, and bimetallic thermal actuator means responsive to the oven temperature having a drive interconnection with said locking member for moving the same into the path of the lever when the latch means is in latched condition and the temperature of the oven above a predetermined degree.

6. The combination set forth in claim 5 wherein the bimetallic member is of coil form, with heating and cooling thereof with the oven causing turning of the locking member between its non-interfering and its locking positions.

7. In an oven and the like equipped with means for heating the interior thereof and having a door, latch means acting between the oven and the door for locking the latter in closed position, mechanical actuator means including an externally accessible operating lever movable by hand to adjust the latch means between the latched and unlatched conditions, a separately movable locking member normal-1y in non-interfering adjacency to the path of movement of said lever, and thermal actuator means including a bimetallic coil responsive to the oven temperature for moving said member into the path of the lever to preclude the movement thereof which adjusts the latch means from the latched condition to preclude unlocking of the door when the temperature is above a predetermined degree.

8. The combination set forth in claim 7, wherein the bimetallic coil is anchored at one end and connected at its other end to a shaft to which said locking member is attached for rotation therewith.

9. The combination set forth in claim 8, wherein the anchored end of the coil is angularly adjustable relative to the other end to vary the coil tension.

10. The combination set forth in claim 7, wherein said one end of the coil is engaged behind an anchoring element which restricts movement of said one end only in the direction followed upon decrease in the temperature of the coil.

References Cited UNITED STATES PATENTS 3,050,048 8/1962. Scott 126273 3,099,471 7/1963 Scott et al 126197 3,125,365 3/1964 Eigelbach 126-197 X 3,176,485 4/1965 Chisholm 126197 X 3,313,918 4/1967 Barber 126-197 X FREDERICK L. MATTESON, JR., Primary Examiner.

E. G. FAVORS, Assistant Examiner. 

